Sometimes its convenient to use the DATA directory, which will be
packaged with the worksheet if you save it (as a .sws file). So for
example you could copy the file to the DATA directory doing something
like:

os.system('cp /full/path/to/list2.txt ' + DATA + 'list2.txt')

and then

f = open(DATA + 'list2.txt')

should work, and would still work if you saved a worksheet copy and
moved it to another computer.

I am tempted to open a ticket in trac for some sort of read_csv
command, which might behave like the following (NOTE: this is just
wishful thinking at this point):